Image lens system

ABSTRACT

This invention provides an image lens system in order from an object side to an image side comprising: a positive first lens element with a convex object-side surface; a negative second lens element; a plastic third lens element with a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a positive plastic fourth lens element with a convex object-side surface and a convex image-side surface, both surfaces thereof being aspheric; and a negative plastic fifth lens element with a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric, at least one inflection point is formed on at least one of the two surfaces thereof; wherein there are air distances between each of lens elements. By such arrangement, not only the photosensitivity and total track length of the system can be reduced, but also better image quality can be obtained.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 100132028 filed in Taiwan, R.O.C. on Sep. 6, 2011, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image lens system, and more particularly, to a compact image lens system used in electronic products.

2. Description of the Prior Art

In recent years, with the popularity of portable electronic products having photographing function, the demand of compact imaging lens system has grown. Generally, the sensor of a general photographing camera is none other than CCD (Charge Coupled Device) or CMOS device (Complementary Metal Oxide Semiconductor device). Furthermore, advances in semiconductor manufacturing technology have allowed the pixel size of sensors to be reduced and therefore lead compact imaging lens systems to higher resolution. In the meantime, the demand for better image quality is also increased.

A conventional imaging lens system with high imaging power, such as the one set forth in U.S. Pat. No. 7,365,920, generally has a front stop and four lens elements; wherein, the first and second lens elements are adhered together to form a doublet for correcting the chromatic aberration. However, this kind of arrangement has the following disadvantages. First, the degree of freedom in arranging the lens system is curtailed due to the employment of excessive number of spherical glass lenses; thus, the total track length of the system cannot be reduced easily. Second, the process of adhering glass lenses together is complicated, posing difficulties in manufacturing. Moreover, the popularity of high-class portable devices such as Smart Phone and PDA (Personal Digital Assistant) drives the rapid improvements in high resolution and image quality of the current compact imaging lens systems, conventional four lens elements systems no longer satisfy the higher level camera modules. On the other hand, although a five-lens-element image system can provide higher resolution to satisfy the current demand for high-end imaging, a conventional image capturing lens system with five lens elements usually has the disadvantage of excessively long total track length, and thereby is not suitable for compact electronic devices.

Inasmuch as the foregoing, a need is continuously existed for a lens system with good image quality and moderate total track length and is suitable for applying for compact and portable electronic products.

SUMMARY OF THE INVENTION

The present invention provides an image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric, at least one inflection point is formed on at least one of the object-side and image-side surfaces thereof; wherein there are air distances between the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and they satisfy the following relations: 0<f/f4<0.95; and 0<T34/T45<2.85.

On the other hand, the present invention provides an image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, a curvature radius of the image-side surface of the third lens element is R6, and they satisfy the following relations: 0<f/f4<0.95; and 0<R6/f<0.78.

Furthermore, the present invention provides an image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric, at least one inflection point is formed on at least one of the object-side and image-side surfaces thereof; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, and they satisfy the following relation: 0<f/f4<0.80.

By such arrangement, not only the photosensitivity and total track length of the system can be reduced, but also better image quality can be obtained.

In the aforementioned image lens system, the first lens element has positive refractive power so that the first lens element can provide refractive power needed for the system and is favorable for reducing the total track length thereof. When the second lens element has negative refractive power, the aberration produced by the first lens element with positive refractive power can be effectively corrected. When the fourth lens element has positive refractive power, the refractive power of the first lens element can be effectively distributed for reducing the sensitivity of the system. Moreover, when the fourth lens element has positive refractive power and the fifth lens element has negative refractive power, a positive-negative telephoto structure is formed so that the back focal length of the system is favorably reduced as well as the total track length thereof is shortened.

In the aforementioned image lens system, the first lens element can be a bi-convex lens element or a meniscus lens element having a convex object-side surface and a concave image-side surface. When the first lens element is a bi-convex lens element, the refractive power of the first lens element can be strengthened for reducing the total track length of the system. When the first lens element is a convex-concave meniscus lens element, it is favorable for correcting the astigmatism of the system. When the second lens element has a concave object-side surface and a concave image-side surface, the aberration of the system can be favorably corrected. When the third lens element has a convex object-side and a concave image-side surface, the ability of correcting the astigmatism of the system can be enhanced, and thereby the image quality can be improved. When the fourth lens element has a convex object-side surface and a convex image-side surface, the refractive power of the fourth lens element can be strengthened effectively for shortening the total track length of the system. When the fifth lens element has a concave image-side surface, the principal point of the system can be positioned away from the image plane, and the back focal length of the system can be reduced as well as the total track length thereof can be shortened favorably for achieving the object of keeping the system compact.

In addition, when at least one inflection is formed on the fifth lens element, the angle at which light projects onto the image sensor from the off-axis field can be effectively reduced so that the sensing efficiency of the image sensor can be improved and the off-axis aberration can be corrected. Furthermore, the arrangement of the lens elements is more suitable for assembly of the system and favorably avoiding the difficulty during assembling when there is air distance between every two lens elements of the present image lens system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an image lens system in accordance with a first embodiment of the present invention.

FIG. 1B shows the aberration curves of the first embodiment of the present invention.

FIG. 2A shows an image lens system in accordance with a second embodiment of the present invention.

FIG. 2B shows the aberration curves of the second embodiment of the present invention.

FIG. 3A shows an image lens system in accordance with a third embodiment of the present invention.

FIG. 3B shows the aberration curves of the third embodiment of the present invention.

FIG. 4A shows an image lens system in accordance with a fourth embodiment of the present invention.

FIG. 4B shows the aberration curves of the fourth embodiment of the present invention.

FIG. 5A shows an image lens system in accordance with a fifth embodiment of the present invention.

FIG. 5B shows the aberration curves of the fifth embodiment of the present invention.

FIG. 6A shows an image lens system in accordance with a sixth embodiment of the present invention.

FIG. 6B shows the aberration curves of the sixth embodiment of the present invention.

FIG. 7A shows an image lens system in accordance with a seventh embodiment of the present invention.

FIG. 7B shows the aberration curves of the seventh embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric, at least one inflection point is formed on at least one of the object-side and image-side surfaces thereof; wherein there are air distances between the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and they satisfy the following relations: 0<f/f4<0.95; and 0<T34/T45<2.85.

When the relation of 0<f/f4<0.95 is satisfied, the refractive power of the fourth lens element is more suitable for effectively controlling the total track length of the system as well as reducing the manufacturing sensitivity thereof; preferably, the following relation is satisfied: 0<f/f4<0.8.

When the relation of 0<T34/T45<2.85 is satisfied, a short spacing distance between lens elements, which results in difficulty in assembly thereof, as well as an excessively long spacing distance between lens elements, which hinders the system from being compact, can be avoided.

In the aforementioned image lens system, the focal length of the image lens system is f, a focal length of the second lens element is f2, and they preferably satisfy the following relation: −0.95<f/f2<0. When the above relation is satisfied, the refractive power of the second lens element is more suitable for favorably correcting the aberration provided by the first lens element and reducing the sensitivity of the system.

In the aforementioned image lens system, an Abbe number of the first lens element is V1, an Abbe number of the second lens element is V2, and they preferably satisfy the following relation: 28<V1−V2<50. When the above relation is satisfied, the chromatic aberration of the system can be corrected favorably.

In the aforementioned image lens system, a curvature radius of the image-side surface of the third lens element is R6, the focal length of the image lens system is f, and they preferably satisfy the following relation: 0<R6/f<0.70. When the above relation is satisfied, suitable refractive power can be obtained by the configuration of the curvature radius of the image-side surface of the third lens element, and thereby the aberration of the system can be favorably corrected as well as the manufacturing sensitivity of thereof can be reduced.

In the aforementioned image lens system, an axial distance between the object-side surface of the first lens element and the image-side surface of the third lens element is D_(r1r6), the focal length of the image lens system is f, and they preferably satisfy the following relation: 0.15<D_(r1r6)/f<0.45. When the above relation is satisfied, the thickness and the spacing distance between lens elements are tighter for keeping the system compact.

On the other hand, the present invention provides an image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, a curvature radius of the image-side surface of the third lens element is R6, and they satisfy the following relations: 0<f/f4<0.95; and 0<R6/f<0.78.

When the relation of 0<f/f4<0.95 is satisfied, the refractive power of the fourth lens element is more suitable for effectively controlling the total track length of the system as well as reducing the manufacturing sensitivity thereof; preferably, the following relation is satisfied: 0<f/f4<0.8.

When the relation of 0<R6/f<0.78 is satisfied, suitable refractive power can be obtained by the configuration of the curvature radius of the image-side surface of the third lens element, and thereby the aberration of the system can be favorably corrected as well as the manufacturing sensitivity of thereof can be reduced; preferably, the following relation is satisfied: 0<R6/f<0.70.

In the aforementioned image lens system, an Abbe number of the first lens element is V1, an Abbe number of the second lens element is V2, and they preferably satisfy the following relation: 28<V1−V2<50. When the above relation is satisfied, the chromatic aberration of the system can be corrected favorably.

In the aforementioned image lens system, an axial distance between the object-side surface of the first lens element and the image-side surface of the third lens element is D_(r1r6), the focal length of the image lens system is f, and they preferably satisfy the following relation: 0.15<D_(r1r6)/f<0.45. When the above relation is satisfied, the thickness and the spacing distance between lens elements are tighter for keeping the system compact.

In the aforementioned image lens system, the system further comprises an image sensor provided on an image plane, an axial distance between the object-side surface of the first lens element and the image plane is TTL, the maximum image height is ImgH, and they preferably satisfy the following relation: TTL/ImgH<1.85. When the above relation is satisfied, it is favorable for keeping the system compact in order to be equipped on portable electronic products.

Furthermore, the present invention provides an image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric, at least one inflection point is formed on at least one of the object-side and image-side surfaces thereof; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, and they satisfy the following relation: 0<f/f4<0.8.

When the relation of 0<f/f4<0.8 is satisfied, the refractive power of the fourth lens element is more suitable for effectively controlling the total track length of the system as well as reducing the manufacturing sensitivity thereof.

In the aforementioned image lens system, a curvature radius of the image-side surface of the third lens element is R6, the focal length of the image lens system is f, and they preferably satisfy the following relation: 0<R6/f<0.78. When the above relation is satisfied, suitable refractive power can be obtained by the configuration of the curvature radius of the image-side surface of the third lens element, and thereby the aberration of the system can be favorably corrected as well as the manufacturing sensitivity of thereof can be reduced.

In the aforementioned image lens system, an axial distance between the object-side surface of the first lens element and the image-side surface of the third lens element is D_(r1r6), the focal length of the image lens system is f, and they preferably satisfy the following relation: 0.15<D_(r1r6)/f<0.45. When the above relation is satisfied, the thickness and the spacing distance between lens elements are tighter for keeping the system compact.

In the aforementioned image lens system, the lens elements can be made of glass or plastic material. If the lens elements are made of glass, the freedom for distributing the refractive power of the image lens system can be increased. If plastic material is adopted to produce the lens elements, the production cost will be reduced effectively. Additionally, the surfaces of the lens elements can be aspheric and easily made into non-spherical profiles, allowing more design parameter freedom which can be used to reduce aberrations and the number of the lens elements used in an optical system. Consequently, the total track length of the image lens system can be effectively reduced.

In the present image lens system, if a lens element has a convex surface, it means the portion of the surface in proximity to the axis is convex; if a lens element has a concave surface, it means the portion of the surface in proximity to the axis is concave.

In the present image lens system, there can be at least one stop, such as a glare stop or a field stop, provided for eliminating stray light and thereby promoting image resolution thereof.

In the present image lens system, the stop can be configured as a front aperture stop or a middle-placed aperture stop. A front aperture stop can provide a longer distance between an exit pupil of the system and an image plane and can improve the image-sensing efficiency of an image sensor of CCD or CMOS. A middle-placed aperture stop is favorable for enlarging the field of view of the system and thereby provides a wide field of view for the same.

Preferred embodiments of the present invention will be described in the following paragraphs by referring to the accompanying drawings.

Embodiment 1

FIG. 1A shows an image lens system in accordance with the first embodiment of the present invention, and FIG. 1B shows the aberration curves of the first embodiment of the present invention. The image lens system of the first embodiment of the present invention mainly comprises five lens elements, in order from an object side to an image side:

a first lens element 110 made of plastic with positive refractive power having a convex object-side surface 111 and a concave image-side surface 112, the object-side and image-side surfaces 111 and 112 thereof being aspheric;

a second lens element 120 made of plastic with negative refractive power having a concave object-side surface 121 and a concave image-side surface 122, the object-side and image-side surfaces 121 and 122 thereof being aspheric;

a third lens element 130 made of plastic with negative refractive power having a convex object-side surface 131 and a concave image-side surface 132, the object-side and image-side surfaces 131 and 132 thereof being aspheric;

a fourth lens element 140 made of plastic with positive refractive power having a convex object-side surface 141 and a convex image-side surface 142, the object-side and image-side surfaces 141 and 142 thereof being aspheric; and

a fifth lens element 150 made of plastic with negative refractive power having a convex object-side surface 151 and a concave image-side surface 152, the object-side and image-side surfaces 151 and 152 thereof being aspheric, and at least one inflection point is formed on both the object-side surface 151 and the image-side surface 152 thereof;

wherein an aperture stop 100 is disposed between the first lens element 110 and the second lens element 120;

the image lens system further comprises an IR filter 160 disposed between the image-side surface 152 of the fifth lens element 150 and an image plane 180, and the IR filter 160 is made of glass and has no influence on the focal length of the image lens system; the image lens system further comprises an image sensor 170 provided on the image plane 180.

The detailed optical data of the first embodiment is shown in TABLE 1, and the aspheric surface data is shown in TABLE 2, wherein the units of the radius of curvature, the thickness and the focal length are expressed in mm, and HFOV is half of the maximal field of view.

TABLE 1 (Embodiment 1) f = 3.74 mm, Fno = 2.65, HFOV = 36.7 deg. Focal Surface # Curvature Radius Thickness Material Index Abbe # length 0 Object Plano Infinity 1 Lens 1   1.697210 (ASP) 0.427 Plastic 1.544 55.9 3.29 2  29.850700 (ASP) −0.027 3 Ape. Stop Plano 0.077 4 Lens 2 −16.730400 (ASP) 0.265 Plastic 1.650 21.4 −10.07 5  10.816600 (ASP) 0.100 6 Lens 3   1.559730 (ASP) 0.265 Plastic 1.650 21.4 −36.20 7   1.364860 (ASP) 0.546 8 Lens 4  11.933200 (ASP) 0.488 Plastic 1.544 55.9 12.56 9 −15.753000 (ASP) 0.526 10 Lens 5   2.211900 (ASP) 0.676 Plastic 1.544 55.9 −12.24 11   1.481520 (ASP) 0.500 12 IR-Filter Plano 0.300 Glass 1.517 64.2 — 13 Plano 0.262 14 Image Plano — * Reference wavelength is d-line 587.6 nm

TABLE 2 Aspheric Coefficients Surface # 1 2 4 5 6 k = −4.14570E+00 −1.00000E+00 1.00000E+01 −1.50000E+01 −1.00000E+00 A4 = −6.61851E−03 −3.92179E−01 8.60813E−03 2.72277E−01 −1.26486E−01 A6 = −5.45783E−02 1.44630E−01 1.93965E−01 −2.95912E−02 1.19529E−01 A8 = −4.04862E−01 9.36894E−01 6.53166E−01 9.64733E−02 −1.86002E−01 A10 = 2.94448E−01 −2.05906E+00 −1.37878E+00 −5.50176E−01 2.23857E−01 A12 = 5.73447E−02 1.31670E+00 9.18112E−01 6.92881E−01 −1.24657E−01 A14 = −4.92705E−02 −5.97188E−06 Surface # 7 8 9 10 11 k = −4.10763E+00 −1.00000E+00 −1.00000E+01 −1.00000E+00 −1.00000E+00 A4 = −4.79740E−03 −4.57619E−02 −1.08622E−01 −2.33623E−01 −1.96785E−01 A6 = 6.03694E−02 2.76086E−02 6.86049E−02 1.37223E−02 5.81740E−02 A8 = −7.42948E−02 −5.89656E−02 −2.23214E−02 2.02470E−02 −1.68741E−02 A10 = 2.62041E−02 6.81831E−02 6.67286E−03 −3.69545E−03 3.35068E−03 A12 = 1.00314E−01 −4.82024E−02 −1.06593E−03 −1.19496E−04 −4.00203E−04 A14 = −8.72652E−02 1.29402E−02 −3.30396E−04 3.04632E−05 2.19570E−05

The equation of the aspheric surface profiles is expressed as follows:

${X(Y)} = {{\left( {Y^{2}/R} \right)/\left( {1 + {{sqrt}\left( {1 - {\left( {1 + k} \right)*\left( {Y/R} \right)^{2}}} \right)}} \right)} + {\sum\limits_{i}{({Ai})*\left( Y^{i} \right)}}}$

wherein:

X: the distance of a point on the aspheric surface at a distance Y from the optical axis relative to the tangential plane at the aspheric surface vertex;

Y: the distance from the point on the curve of the aspheric surface to the optical axis;

R: curvature radius k: the conic coefficient;

Ai: the aspheric coefficient of order i.

In the first embodiment of the present image lens system, the focal length of the image lens system is f, and it satisfies the following relation: f=3.74 (mm).

In the first embodiment of the present image lens system, the f-number of the image lens system is Fno, and it satisfies the relation: Fno=2.65.

In the first embodiment of the present image lens system, half of the maximal field of view of the image lens system is HFOV, and it satisfies the relation: HFOV=36.7 deg.

In the first embodiment of the present image lens system, an Abbe number of the first lens element 110 is V1, an Abbe number of the second lens element 120 is V2, and they satisfy the following relation: V1−V2=34.5.

In the first embodiment of the present image lens system, an axial distance between the third lens element 130 and the fourth lens element 140 is T34, an axial distance between the fourth lens element 140 and the fifth lens element 150 is T45, and they satisfy the following relation: T34/T45=1.04.

In the first embodiment of the present image lens system, a curvature radius of the image-side surface 132 of the third lens element 130 is R6, the focal length of the image lens system is f, and they satisfy the following relation: R6/f=0.36.

In the first embodiment of the present image lens system, the focal length of the image lens system is f, a focal length of the second lens element 120 is f2, and they satisfy the following relation: f/f2=−0.37.

In the first embodiment of the present image lens system, the focal length of the image lens system is f, a focal length of the fourth lens element 140 is f4, and they satisfy the following relation: f/f4=0.30.

In the first embodiment of the present image lens system, an axial distance between the object-side surface 111 of the first lens element 110 and the image-side surface 132 of the third lens element 130 is D_(r1r6), the focal length of the image lens system is f, and they satisfy the following relation: D_(r1r6)/f=0.30.

In the first embodiment of the present image lens system, an axial distance between the object-side surface 111 of the first lens element 110 and the image plane 180 is TTL, the maximum image height of the image lens system, which is defined here as a half of a diagonal length of an effective photosensitive area of the image sensor 170 is ImgH, and they satisfy the following relation: TTL/ImgH=1.54.

Embodiment 2

FIG. 2A shows an image lens system in accordance with the second embodiment of the present invention, and FIG. 2B shows the aberration curves of the second embodiment of the present invention. The image lens system of the second embodiment of the present invention mainly comprises five lens elements, in order from an object side to an image side:

a first lens element 210 made of plastic with positive refractive power having a convex object-side surface 211 and a convex image-side surface 212, the object-side and image-side surfaces 211 and 212 thereof being aspheric;

a second lens element 220 made of plastic with negative refractive power having a concave object-side surface 221 and a concave image-side surface 222, the object-side and image-side surfaces 221 and 222 thereof being aspheric;

a third lens element 230 made of plastic with positive refractive power having a convex object-side surface 231 and a concave image-side surface 232, the object-side and image-side surfaces 231 and 232 thereof being aspheric;

a fourth lens element 240 made of plastic with positive refractive power having a convex object-side surface 241 and a convex image-side surface 242, the object-side and image-side surfaces 241 and 242 thereof being aspheric; and

a fifth lens element 250 made of plastic with negative refractive power having a convex object-side surface 251 and a concave image-side surface 252, the object-side and image-side surfaces 251 and 252 thereof being aspheric, and at least one inflection point is formed on both the object-side surface 251 and the image-side surface 252 thereof;

wherein an aperture stop 200 is disposed between the first lens element 210 and the second lens element 220;

the image lens system further comprises an IR filter 260 disposed between the image-side surface 252 of the fifth lens element 250 and an image plane 280, and the IR filter 260 is made of glass and has no influence on the focal length of the image lens system; the image lens system further comprises an image sensor 270 provided on the image plane 280.

The detailed optical data of the second embodiment is shown in TABLE 3, and the aspheric surface data is shown in TABLE 4, wherein the units of the radius of curvature, the thickness and the focal length are expressed in mm, and HFOV is half of the maximal field of view.

TABLE 3 (Embodiment 2) f = 3.77 mm, Fno = 2.60, HFOV = 36.7 deg. Focal Surface # Curvature Radius Thickness Material Index Abbe # length 0 Object Plano Infinity 1 Lens 1   1.691570 (ASP) 0.449 Plastic 1.544 55.9 2.83 2 −15.704000 (ASP) −0.041 3 Ape. Stop Plano 0.091 4 Lens 2  −6.446300 (ASP) 0.265 Plastic 1.607 26.6 −4.02 5   3.997800 (ASP) 0.161 6 Lens 3   1.332660 (ASP) 0.279 Plastic 1.544 55.9 11.64 7   1.563430 (ASP) 0.616 8 Lens 4   9.637600 (ASP) 0.429 Plastic 1.544 55.9 9.88 9 −11.973200 (ASP) 0.549 10 Lens 5   2.705680 (ASP) 0.603 Plastic 1.544 55.9 −7.02 11   1.459690 (ASP) 0.400 12 IR-Filter Plano 0.300 Glass 1.517 64.2 — 13 Plano 0.305 14 Image Plano — * Reference wavelength is d-line 587.6 nm

TABLE 4 Aspheric Coefficients Surface # 1 2 4 5 6 k = −3.09185E+00 −1.00000E+00 −3.03770E+00 −1.49912E+01 −1.00000E+00 A4 = −1.32003E−02 −2.18025E−01 1.31150E−01 2.33486E−01 −1.28268E−01 A6 = −5.72652E−02 −6.64144E−02 −6.67090E−02 −1.05388E−02 1.41129E−01 A8 = −2.82200E−01 6.65974E−01 3.92497E−01 −1.32784E−01 −1.23680E−01 A10 = 2.24837E−01 −1.15850E+00 −2.26475E−01 1.30429E−01 3.91273E−02 A12 = −2.15313E−01 6.98436E−01 1.35838E−02 6.09018E−02 3.83758E−03 A14 = 1.94330E−01 −5.12475E−06 Surface # 7 8 9 10 11 k = −2.28878E+00 −1.00000E+00 1.00000E+01 −1.00000E+00 −1.00000E+00 A4 = −4.01644E−02 −3.20094E−02 −4.18269E−02 −2.14203E−01 −2.01317E−01 A6 = 5.21506E−02 1.87395E−02 1.13696E−02 3.26143E−03 5.69734E−02 A8 = −3.09398E−02 −1.33942E−01 −3.20276E−02 2.29132E−02 −1.54767E−02 A10 = −9.77103E−03 1.10591E−01 1.62153E−02 −3.61726E−03 3.16374E−03 A12 = 2.91530E−03 −2.29721E−02 1.47472E−03 −2.12319E−04 −4.28025E−04 A14 = 5.90981E−03 −1.13837E−02 −1.56983E−03 3.45652E−05 2.68940E−05

The equation of the aspheric surface profiles of the second embodiment has the same form as that of the first embodiment. Moreover, the description of the factors in the relations is as those set forth in the first embodiment, but the values of the relations of the second embodiment are listed in the following TABLE 5.

TABLE 5 Embodiment 2 f 3.77 R6/f 0.42 Fno 2.60 f/f2 −0.94 HFOV 36.7 f/f4 0.38 V1 − V2 29.3 D_(r1r6)/f 0.32 T34/T45 1.12 TTL/ImgH 1.54

Embodiment 3

FIG. 3A shows an image lens system in accordance with the third embodiment of the present invention, and FIG. 3B shows the aberration curves of the third embodiment of the present invention. The image lens system of the third embodiment of the present invention mainly comprises five lens elements, in order from an object side to an image side:

a first lens element 310 made of plastic with positive refractive power having a convex object-side surface 311 and a concave image-side surface 312, the object-side and image-side surfaces 311 and 312 thereof being aspheric;

a second lens element 320 made of plastic with negative refractive power having a concave object-side surface 321 and a concave image-side surface 322, the object-side and image-side surfaces 321 and 322 thereof being aspheric;

a third lens element 330 made of plastic with positive refractive power having a convex object-side surface 331 and a concave image-side surface 332, the object-side and image-side surfaces 331 and 332 thereof being aspheric;

a fourth lens element 340 made of plastic with positive refractive power having a convex object-side surface 341 and a convex image-side surface 342, the object-side and image-side surfaces 341 and 342 thereof being aspheric; and

a fifth lens element 350 made of plastic with negative refractive power having a convex object-side surface 351 and a concave image-side surface 352, the object-side and image-side surfaces 351 and 352 thereof being aspheric, and at least one inflection point is formed on both the object-side surface 351 and the image-side surface 352 thereof;

wherein an aperture stop 300 is disposed between an imaged object and the first lens element 310;

the image lens system further comprises an IR filter 360 disposed between the image-side surface 352 of the fifth lens element 350 and an image plane 380, and the IR filter 360 is made of glass and has no influence on the focal length of the image lens system; the image lens system further comprises an image sensor 370 provided on the image plane 380.

The detailed optical data of the third embodiment is shown in TABLE 6, and the aspheric surface data is shown in TABLE 7, wherein the units of the radius of curvature, the thickness and the focal length are expressed in mm, and HFOV is half of the maximal field of view.

TABLE 6 (Embodiment 3) f = 4.17 mm, Fno = 2.50, HFOV = 33.8 deg. Focal Surface # Curvature Radius Thickness Material Index Abbe # length 0 Object Plano Infinity 1 Ape. Stop Plano −0.163 2 Lens 1   1.678470 (ASP) 0.543 Plastic 1.544 55.9 3.14 3  91.219900 (ASP) 0.053 4 Lens 2  −6.218900 (ASP) 0.275 Plastic 1.634 23.8 −5.22 5   7.196700 (ASP) 0.116 6 Lens 3   1.831420 (ASP) 0.300 Plastic 1.544 55.9 19.39 7   2.088230 (ASP) 0.745 8 Lens 4  18.747000 (ASP) 0.525 Plastic 1.544 55.9 7.35 9  −5.036600 (ASP) 0.386 10 Lens 5   5.077300 (ASP) 0.758 Plastic 1.544 55.9 −4.71 11   1.612950 (ASP) 0.500 12 IR-Filter Plano 0.300 Glass 1.517 64.2 — 13 Plano 0.301 14 Image Plano — * Reference wavelength is d-line 587.6 nm

TABLE 7 Aspheric Coefficients Surface # 2 3 4 5 6 k = −7.05254E−01 −1.00000E+00 −1.50000E+01 −1.00000E+00 −3.95369E−02 A4 = −1.25467E−02 −5.65578E−02 1.84461E−01 1.52644E−01 −2.23941E−01 A6 = −1.82267E−02 −6.48656E−02 −1.99966E−01 2.20685E−02 1.99159E−01 A8 = −5.05250E−02 −4.08190E−02 1.85573E−01 −1.57059E−02 −1.91040E−01 A10 = 3.41161E−02 1.28560E−01 −7.92357E−02 −1.64554E−02 1.63121E−01 A12 = −4.87213E−02 −9.36928E−02 1.23022E−02 6.49850E−03 −4.40342E−02 Surface # 7 8 9 10 11 k = −2.33181E+00 −1.00000E+00 2.09657E+00 −1.00000E+00 −3.27323E+00 A4 = −1.15345E−01 2.02838E−03 −4.79242E−02 −2.55879E−01 −1.54790E−01 A6 = 3.18188E−02 −4.03546E−03 4.82762E−05 1.73881E−02 6.77337E−02 A8 = 3.54952E−02 −7.92789E−02 3.80681E−03 2.67690E−02 −2.34675E−02 A10 = −4.41982E−02 1.08820E−01 7.04317E−03 −4.57554E−03 5.19227E−03 A12 = 3.08851E−02 −6.40046E−02 −2.98579E−03 1.28609E−04 −6.41551E−04 A14 = 5.62641E−03 1.31469E−02 1.50779E−04 −1.40231E−04 3.25239E−05

The equation of the aspheric surface profiles of the third embodiment has the same form as that of the first embodiment. Moreover, the description of the factors in the relations is as those set forth in the first embodiment, but the values of the relations of the third embodiment are listed in the following TABLE 8.

TABLE 8 Embodiment 3 f 4.17 R6/f 0.50 Fno 2.50 f/f2 −0.80 HFOV 33.8 f/f4 0.57 V1 − V2 32.1 D_(r1r6)/f 0.31 T34/T45 1.93 TTL/ImgH 1.68

Embodiment 4

FIG. 4A shows an image lens system in accordance with the fourth embodiment of the present invention, and FIG. 4B shows the aberration curves of the fourth embodiment of the present invention. The image lens system of the fourth embodiment of the present invention mainly comprises five lens elements, in order from an object side to an image side:

a first lens element 410 made of plastic with positive refractive power having a convex object-side surface 411 and a convex image-side surface 412, the object-side and image-side surfaces 411 and 412 thereof being aspheric;

a second lens element 420 made of plastic with negative refractive power having a concave object-side surface 421 and a convex image-side surface 422, the object-side and image-side surfaces 421 and 422 thereof being aspheric;

a third lens element 430 made of plastic with negative refractive power having a convex object-side surface 431 and a concave image-side surface 432, the object-side and image-side surfaces 431 and 432 thereof being aspheric;

a fourth lens element 440 made of plastic with positive refractive power having a convex object-side surface 441 and a convex image-side surface 442, the object-side and image-side surfaces 441 and 442 thereof being aspheric; and

a fifth lens element 450 made of plastic with negative refractive power having a convex object-side surface 451 and a concave image-side surface 452, the object-side and image-side surfaces 451 and 452 thereof being aspheric, and at least one inflection point is formed on both the object-side surface 451 and the image-side surface 452 thereof;

wherein an aperture stop 400 is disposed between an imaged object and the first lens element 410;

the image lens system further comprises an IR filter 460 disposed between the image-side surface 452 of the fifth lens element 450 and an image plane 480, and the IR filter 460 is made of glass and has no influence on the focal length of the image lens system; the image lens system further comprises an image sensor 470 provided on the image plane 480.

The detailed optical data of the fourth embodiment is shown in TABLE 9, and the aspheric surface data is shown in TABLE 10, wherein the units of the radius of curvature, the thickness and the focal length are expressed in mm, and HFOV is half of the maximal field of view.

TABLE 9 (Embodiment 4) f = 4.07 mm, Fno = 2.50, HFOV = 34.5 deg. Focal Surface # Curvature Radius Thickness Material Index Abbe # length 0 Object Plano Infinity 1 Ape. Stop Plano −0.134 2 Lens 1   1.713760 (ASP) 0.546 Plastic 1.544 55.9 2.97 3 −24.547400 (ASP) 0.100 4 Lens 2  −3.246400 (ASP) 0.255 Plastic 1.634 23.8 −6.50 5 −15.804800 (ASP) 0.124 6 Lens 3   3.003200 (ASP) 0.334 Plastic 1.634 23.8 −36.01 7   2.539540 (ASP) 0.619 8 Lens 4  15.674000 (ASP) 0.577 Plastic 1.544 55.9 5.64 9  −3.765400 (ASP) 0.454 10 Lens 5   4.570500 (ASP) 0.691 Plastic 1.544 55.9 −4.36 11   1.478040 (ASP) 0.500 12 IR-Filter Plano 0.300 Glass 1.517 64.2 — 13 Plano 0.303 14 Image Plano — * Reference wavelength is d-line 587.6 nm

TABLE 10 Aspheric Coefficients Surface # 2 3 4 5 6 k = −5.48198E−01 −1.00000E+00 −5.86979E+00 −1.00000E+00 −1.62681E+00 A4 = −7.26917E−03 −4.88649E−02 1.80277E−01 1.43262E−01 −2.33951E−01 A6 = −2.01383E−02 −5.29343E−02 −1.91219E−01 −9.74449E−03 1.90369E−01 A8 = −4.98978E−02 −5.97358E−02 1.77025E−01 −1.93519E−02 −1.99128E−01 A10 = 5.18816E−02 1.12644E−01 −9.84851E−02 −5.18966E−03 1.37148E−01 A12 = −8.09860E−02 −8.97977E−02 2.30669E−02 −3.22061E−02 −5.29703E−02 Surface # 7 8 9 10 11 k = −8.20615E+00 −1.00000E+00 −8.84594E−01 −1.00000E+00 −3.44593E+00 A4 = −1.16002E−01 2.09601E−03 −2.83974E−02 −2.50198E−01 −1.52587E−01 A6 = 4.52361E−02 −2.14914E−03 −4.42188E−03 2.30280E−02 6.78515E−02 A8 = 2.67286E−02 −8.05227E−02 1.59642E−03 2.24579E−02 −2.36587E−02 A10 = −5.31356E−02 1.08120E−01 6.86182E−03 −5.43873E−03 5.19056E−03 A12 = 2.78312E−02 −6.25864E−02 −2.88267E−03 2.21535E−04 −6.32614E−04 A14 = 9.75389E−03 1.32587E−02 3.46527E−04 1.25201E−05 3.19528E−05

The equation of the aspheric surface profiles of the fourth embodiment has the same form as that of the first embodiment. Moreover, the description of the factors in the relations is as those set forth in the first embodiment, but the values of the relations of the fourth embodiment are listed in the following TABLE 11.

TABLE 11 Embodiment 4 f 4.07 R6/f 0.62 Fno 2.50 f/f2 −0.63 HFOV 34.5 f/f4 0.72 V1 − V2 32.5 D_(r1r6)/f 0.33 T34/T45 1.36 TTL/ImgH 1.68

Embodiment 5

FIG. 5A shows an image lens system in accordance with the fifth embodiment of the present invention, and FIG. 5B shows the aberration curves of the fifth embodiment of the present invention. The image lens system of the fifth embodiment of the present invention mainly comprises five lens elements, in order from an object side to an image side:

a first lens element 510 made of plastic with positive refractive power having a convex object-side surface 511 and a convex image-side surface 512, the object-side and image-side surfaces 511 and 512 thereof being aspheric;

a second lens element 520 made of plastic with negative refractive power having a concave object-side surface 521 and a concave image-side surface 522, the object-side and image-side surfaces 521 and 522 thereof being aspheric;

a third lens element 530 made of plastic with positive refractive power having a convex object-side surface 531 and a concave image-side surface 532, the object-side and image-side surfaces 531 and 532 thereof being aspheric;

a fourth lens element 540 made of plastic with positive refractive power having a convex object-side surface 541 and a convex image-side surface 542, the object-side and image-side surfaces 541 and 542 thereof being aspheric; and

a fifth lens element 550 made of plastic with negative refractive power having a convex object-side surface 551 and a concave image-side surface 552, the object-side and image-side surfaces 551 and 552 thereof being aspheric, and at least one inflection point is formed on both the object-side surface 551 and the image-side surface 552 thereof;

wherein an aperture stop 500 is disposed between an imaged object and the first lens element 510;

the image lens system further comprises an IR filter 560 disposed between the image-side surface 552 of the fifth lens element 550 and an image plane 580, and the IR filter 560 is made of glass and has no influence on the focal length of the image lens system; the image lens system further comprises an image sensor 570 provided on the image plane 580.

The detailed optical data of the fifth embodiment is shown in TABLE 12, and the aspheric surface data is shown in TABLE 13, wherein the units of the radius of curvature, the thickness and the focal length are expressed in mm, and HFOV is half of the maximal field of view.

TABLE 12 (Embodiment 5) f = 3.78 mm, Fno = 2.60, HFOV = 36.1 deg. Focal Surface # Curvature Radius Thickness Material Index Abbe # length 0 Object Plano Infinity 1 Ape. Stop Plano −0.082 2 Lens 1 1.737860 (ASP) 0.581 Plastic 1.535 56.3 2.66 3 −6.913400 (ASP)   0.120 4 Lens 2 −3.972800 (ASP)   0.270 Plastic 1.634 23.8 −4.25 5 8.614400 (ASP) 0.225 6 Lens 3 2.806260 (ASP) 0.286 Plastic 1.634 23.8 57.28 7 2.921000 (ASP) 0.509 8 Lens 4 15.674000 (ASP)  0.637 Plastic 1.544 55.9 4.36 9 −2.753920 (ASP)   0.258 10 Lens 5 3.602700 (ASP) 0.606 Plastic 1.535 56.3 3.59 11 1.178860 (ASP) 0.500 12 IR-Filter Plano 0.300 Glass 1.517 64.2 — 13 Plano 0.302 14 Image Plano — * Reference wavelength is d-line 587.6 nm

TABLE 13 Aspheric Coefficients Surface # 2 3 4 5 6 k = −6.70197E−01 −1.00000E+00 −2.68806E+00 −1.00000E+00 −2.31563E+00 A4 = −1.06725E−02 −1.51114E−02 1.72078E−01 1.08511E−01 −2.35188E−01 A6 = −4.16175E−02 −1.20350E−01 −2.40402E−01 −3.56692E−02 1.85714E−01 A8 = −9.02852E−03 −4.89283E−02 1.36533E−01 −6.14849E−02 −2.17860E−01 A10 = −1.05101E−02 8.78696E−02 −5.44906E−02 3.34638E−02 1.30123E−01 A12 = −1.00772E−01 −7.88191E−02 6.36160E−02 −1.17100E−02 −6.08407E−02 Surface # 7 8 9 10 11 k = −1.50000E+01 −1.00000E+00 −1.00000E+01 −1.00000E+00 −3.87902E+00 A4 = −1.31673E−01 2.87588E−02 −1.65145E−02 −2.87781E−01 −1.49626E−01 A6 = 3.52299E−02 −1.38406E−02 −1.86529E−03 4.99728E−02 6.77456E−02 A8 = 2.10610E−02 −8.12290E−02 1.29634E−03 2.22967E−02 −2.33847E−02 A10 = −5.78635E−02 1.07320E−01 6.45625E−03 −6.09795E−03 5.13285E−03 A12 = 1.81800E−02 −6.21122E−02 −3.19670E−03 6.40792E−05 −6.44227E−04 A14 = 1.95960E−02 1.30017E−02 2.65673E−04 −3.20018E−05 3.44618E−05

The equation of the aspheric surface profiles of the fifth embodiment has the same form as that of the first embodiment. Moreover, the description of the factors in the relations is as those set forth in the first embodiment, but the values of the relations of the fifth embodiment are listed in the following TABLE 14.

TABLE 14 Embodiment 5 f 3.78 R6/f 0.77 Fno 2.60 f/f2 −0.89 HFOV 36.1 f/f4 0.87 V1 − V2 32.5 D_(r1r6)/f 0.39 T34/T45 1.97 TTL/ImgH 1.63

Embodiment 6

FIG. 6A shows an image lens system in accordance with the sixth embodiment of the present invention, and FIG. 6B shows the aberration curves of the sixth embodiment of the present invention. The image lens system of the sixth embodiment of the present invention mainly comprises five lens elements, in order from an object side to an image side:

a first lens element 610 made of glass with positive refractive power having a convex object-side surface 611 and a concave image-side surface 612, the object-side and image-side surfaces 611 and 612 thereof being aspheric;

a second lens element 620 made of plastic with negative refractive power having a concave object-side surface 621 and a concave image-side surface 622, the object-side and image-side surfaces 621 and 622 thereof being aspheric;

a third lens element 630 made of plastic with positive refractive power having a convex object-side surface 631 and a concave image-side surface 632, the object-side and image-side surfaces 631 and 632 thereof being aspheric;

a fourth lens element 640 made of plastic with positive refractive power having a convex object-side surface 641 and a convex image-side surface 642, the object-side and image-side surfaces 641 and 642 thereof being aspheric; and

a fifth lens element 650 made of plastic with negative refractive power having a concave object-side surface 651 and a concave image-side surface 652, the object-side and image-side surfaces 651 and 652 thereof being aspheric, and at least one inflection point is formed on the image-side surface 652 thereof;

wherein an aperture stop 600 is disposed between an imaged object and the first lens element 610;

the image lens system further comprises an IR filter 660 disposed between the image-side surface 652 of the fifth lens element 650 and an image plane 680, and the IR filter 660 is made of glass and has no influence on the focal length of the image lens system; the image lens system further comprises an image sensor 670 provided on the image plane 680.

The detailed optical data of the sixth embodiment is shown in TABLE 15, and the aspheric surface data is shown in TABLE 16, wherein the units of the radius of curvature, the thickness and the focal length are expressed in mm, and HFOV is half of the maximal field of view.

TABLE 15 (Embodiment 6) f = 4.23 mm, Fno = 2.50, HFOV = 33.5 deg. Focal Surface # Curvature Radius Thickness Material Index Abbe # length 0 Object Plano Infinity 1 Ape. Stop Plano −0.192 2 Lens 1   1.573280 (ASP) 0.522 Glass 1.569 71.3 3.30 3   8.577600 (ASP) 0.103 4 Lens 2 −11.791100 (ASP) 0.275 Plastic 1.634 23.8 −7.13 5   7.390800 (ASP) 0.130 6 Lens 3   2.067250 (ASP) 0.275 Plastic 1.544 55.9 77.50 7   2.071910 (ASP) 0.707 8 Lens 4  18.747000 (ASP) 0.559 Plastic 1.544 55.9 5.39 9  −3.443700 (ASP) 0.387 10 Lens 5 −30.918200 (ASP) 0.685 Plastic 1.544 55.9 −3.82 11   2.246120 (ASP) 0.500 12 IR-Filter Plano 0.300 Glass 1.517 64.2 — 13 Plano 0.304 14 Image Plano — * Reference wavelength is d-line 587.6 nm

TABLE 16 Aspheric Coefficients Surface # 2 3 4 5 6 k = −5.24072E−01 −1.00000E+00 8.62106E+00 −1.00000E+00 −1.64890E+00 A4 = −6.00458E−03 −3.19196E−02 1.79681E−01 1.29569E−01 −2.57074E−01 A6 = −1.73646E−02 −1.01897E−01 −1.90074E−01 4.24791E−02 1.92882E−01 A8 = −4.22009E−02 −2.79502E−02 1.93282E−01 2.26998E−02 −1.71504E−01 A10 = 2.11808E−02 1.25143E−01 −5.50384E−02 2.42155E−02 1.91775E−01 A12 = −3.86145E−02 −8.38965E−02 −2.50030E−03 −1.50838E−02 −3.99901E−02 Surface # 7 8 9 10 11 k = −5.15045E+00 −1.00000E+00 −3.96485E+00 −1.00000E+00 −9.55826E−01 A4 = −1.29521E−01 3.74251E−03 5.10663E−03 −1.70262E−01 −1.62983E−01 A6 = 3.33587E−02 2.22491E−02 −1.10455E−02 1.17488E−02 6.12811E−02 A8 = 3.92944E−02 −1.00815E−01 4.50787E−03 1.99730E−02 −2.10808E−02 A10 = −2.98986E−02 1.10100E−01 6.27601E−03 −3.69322E−03 4.96922E−03 A12 = 3.66977E−02 −5.83441E−02 −3.35486E−03 6.30742E−04 −6.85044E−04 A14 = 4.24777E−04 1.15391E−02 3.16525E−04 −2.48583E−04 3.98711E−05

The equation of the aspheric surface profiles of the sixth embodiment has the same form as that of the first embodiment. Moreover, the description of the factors in the relations is as those set forth in the first embodiment, but the values of the relations of the sixth embodiment are listed in the following TABLE 17.

TABLE 17 Embodiment 6 f 4.23 R6/f 0.49 Fno 2.50 f/f2 −0.59 HFOV 33.5 f/f4 0.78 V1 − V2 47.5 D_(r1r6)/f 0.31 T34/T45 1.83 TTL/ImgH 1.66

Embodiment 7

FIG. 7A shows an image lens system in accordance with the seventh embodiment of the present invention, and FIG. 7B shows the aberration curves of the seventh embodiment of the present invention. The image lens system of the seventh embodiment of the present invention mainly comprises five lens elements, in order from an object side to an image side:

a first lens element 710 made of glass with positive refractive power having a convex object-side surface 711 and a concave image-side surface 712, the object-side and image-side surfaces 711 and 712 thereof being aspheric;

a second lens element 720 made of plastic with negative refractive power having a convex object-side surface 721 and a concave image-side surface 722, the object-side and image-side surfaces 721 and 722 thereof being aspheric;

a third lens element 730 made of plastic with positive refractive power having a convex object-side surface 731 and a concave image-side surface 732, the object-side and image-side surfaces 731 and 732 thereof being aspheric;

a fourth lens element 740 made of plastic with positive refractive power having a convex object-side surface 741 and a convex image-side surface 742, the object-side and image-side surfaces 741 and 742 thereof being aspheric; and

a fifth lens element 750 made of plastic with negative refractive power having a concave object-side surface 751 and a concave image-side surface 752, the object-side and image-side surfaces 751 and 752 thereof being aspheric, and at least one inflection point is formed on the image-side surface 752 thereof;

wherein an aperture stop 700 is disposed between an imaged object and the first lens element 710;

the image lens system further comprises an IR filter 760 disposed between the image-side surface 752 of the fifth lens element 750 and an image plane 780, and the IR filter 760 is made of glass and has no influence on the focal length of the image lens system; the image lens system further comprises an image sensor 770 provided on the image plane 780.

The detailed optical data of the seventh embodiment is shown in TABLE 18, and the aspheric surface data is shown in TABLE 19, wherein the units of the radius of curvature, the thickness and the focal length are expressed in mm, and HFOV is half of the maximal field of view.

TABLE 18 (Embodiment 7) f = 4.25 mm, Fno = 2.55, HFOV = 33.3 deg. Focal Surface # Curvature Radius Thickness Material Index Abbe # length 0 Object Plano Infinity 1 Ape. Stop Plano −0.185 2 Lens 1   1.576490 (ASP) 0.510 Glass 1.569 71.3 3.62 3   5.929800 (ASP) 0.094 4 Lens 2  29.411800 (ASP) 0.275 Plastic 1.634 23.8 −8.89 5   4.713800 (ASP) 0.141 6 Lens 3   1.971460 (ASP) 0.275 Plastic 1.544 55.9 79.23 7   1.964380 (ASP) 0.711 8 Lens 4  18.515600 (ASP) 0.535 Plastic 1.544 55.9 5.43 9  −3.478400 (ASP) 0.395 10 Lens 5 −30.918200 (ASP) 0.678 Plastic 1.535 56.3 −3.94 11   2.280110 (ASP) 0.400 12 IR-Filter Plano 0.300 Glass 1.517 64.2 — 13 Plano 0.421 14 Image Plano — * Reference wavelength is d-line 587.6 nm

TABLE 19 Aspheric Coefficients Surface # 2 3 4 5 6 k = −5.88792E−01 −1.00000E+00 −1.50000E+01 −1.00000E+00 −1.50220E+00 A4 = −8.76870E−03 −3.09057E−02 1.78065E−01 1.29906E−01 −2.55361E−01 A6 = −1.81272E−02 −1.02633E−01 −1.91100E−01 4.34846E−02 1.93404E−01 A8 = −4.06312E−02 −2.85102E−02 1.91969E−01 2.37611E−02 −1.71055E−01 A10 = 2.52073E−02 1.25571E−01 −5.68565E−02 2.50184E−02 1.92814E−01 A12 = −3.45227E−02 −8.29946E−02 −3.89833E−03 −1.46225E−02 −3.90348E−02 Surface # 7 8 9 10 11 k = −4.92950E+00 −1.00000E+00 −4.41840E+00 −1.00000E+00 −9.60473E−01 A4 = −1.29110E−01 3.82694E−03 6.14128E−03 −1.69575E−01 −1.62918E−01 A6 = 3.32451E−02 2.12856E−02 −1.07511E−02 1.18945E−02 6.09555E−02 A8 = 3.93013E−02 −1.01102E−01 4.54042E−03 1.99962E−02 −2.11131E−02 A10 = −3.00141E−02 1.10067E−01 6.27125E−03 −3.68653E−03 4.96811E−03 A12 = 3.66262E−02 −5.83205E−02 −3.35996E−03 6.33162E−04 −6.84575E−04 A14 = 1.37904E−04 1.15645E−02 3.13978E−04 −2.47705E−04 4.00487E−05

The equation of the aspheric surface profiles of the seventh embodiment has the same form as that of the first embodiment. Moreover, the description of the factors in the relations is as those set forth in the first embodiment, but the values of the relations of the seventh embodiment are listed in the following TABLE 20.

TABLE 20 Embodiment 7 f 4.25 R6/f 0.46 Fno 2.55 f/f2 −0.48 HFOV 33.3 f/f4 0.78 V1 − V2 47.5 D_(r1r6)/f 0.30 T34/T45 1.80 TTL/ImgH 1.65

It is to be noted that TABLES 1-20 show different data of the different embodiments, however, the data of the different embodiments are obtained from experiments. Therefore, any image lens system of the same structure is considered to be within the scope of the present invention even if it uses different data. The embodiments depicted above and the appended drawings are exemplary and are not intended to limit the scope of the present invention. 

1. An image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric, at least one inflection point is formed on at least one of the object-side and image-side surfaces thereof; wherein there are air distances between the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and they satisfy the following relations: 0<f/f4<0.95; and 0<T34/T45<2.85.
 2. The image lens system according to claim 1, wherein the third lens element has a convex object-side surface.
 3. The image lens system according to claim 2, wherein the focal length of the image lens system is f, a focal length of the second lens element is f2, and they satisfy the following relation: −0.95<f/f2<0.
 4. The image lens system according to claim 3, wherein an Abbe number of the first lens element is V1, an Abbe number of the second lens element is V2, and they satisfy the following relation: 28<V1−V2<50.
 5. The image lens system according to claim 3, wherein the second lens element has a concave object-side surface and a concave image-side surface.
 6. The image lens system according to claim 2, wherein a curvature radius of the image-side surface of the third lens element is R6, the focal length of the image lens system is f, and they satisfy the following relation: 0<R6/f<0.70.
 7. The image lens system according to claim 2, wherein the focal length of the image lens system is f, the focal length of the fourth lens element is f4, and they satisfy the following relation: 0<f/f4<0.8.
 8. The image lens system according to claim 2, wherein an axial distance between the object-side surface of the first lens element and the image-side surface of the third lens element is D_(r1r6), the focal length of the image lens system is f, and they satisfy the following relation: 0.15<D _(r1r6) /f<0.45.
 9. An image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, a curvature radius of the image-side surface of the third lens element is R6, and they satisfy the following relations: 0<f/f4<0.95; and 0<R6/f<0.78.
 10. The image lens system according to claim 9, wherein the third lens element has a convex object-side surface, and at least one inflection point is formed on at least one of the object-side and image-side surfaces of the fifth lens element.
 11. The image lens system according to claim 10, wherein the focal length of the image lens system is f, the focal length of the fourth lens element is f4, and they satisfy the following relation: 0<f/f4<0.8.
 12. The image lens system according to claim 10, wherein a curvature radius of the image-side surface of the third lens element is R6, the focal length of the image lens system is f, and they satisfy the following relation: 0<R6/f<0.70.
 13. The image lens system according to claim 10, wherein an Abbe number of the first lens element is V1, an Abbe number of the second lens element is V2, and they satisfy the following relation: 28<V1−V2<50.
 14. The image lens system according to claim 10, wherein an axial distance between the object-side surface of the first lens element and the image-side surface of the third lens element is D_(r1r6), the focal length of the image lens system is f, and they satisfy the following relation: 0.15<D _(r1r6) /f<0.45.
 15. The image lens system according to claim 10, further comprising an image sensor provided on an image plane, an axial distance between the object-side surface of the first lens element and the image plane is TTL, the maximum image height of the image lens system is ImgH, and they satisfy the following relation: TTL/ImgH<1.85.
 16. An image lens system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a plastic third lens element having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric; a plastic fourth lens element with positive refractive power having a convex object-side surface and a convex image-side surface, both the object-side and image-side surfaces thereof being aspheric; and a plastic fifth lens element with negative refractive power having a concave image-side surface, both the object-side and image-side surfaces thereof being aspheric, at least one inflection point is formed on at least one of the object-side and image-side surfaces thereof; wherein a focal length of the image lens system is f, a focal length of the fourth lens element is f4, and they satisfy the following relation: 0<f/f4<0.80.
 17. The image lens system according to claim 16, wherein the third lens element has a convex object-side surface.
 18. The image lens system according to claim 16, wherein the second lens element has a concave object-side surface and a concave image-side surface.
 19. The image lens system according to claim 16, wherein a curvature radius of the image-side surface of the third lens element is R6, the focal length of the image lens system is f, and they satisfy the following relation: 0<R6/f<0.78.
 20. The image lens system according to claim 16, wherein an axial distance between the object-side surface of the first lens element and the image-side surface of the third lens element is D_(r1r6), the focal length of the image lens system is f, and they satisfy the following relation: 0.15<D _(r1r6) /f<0.45. 